Typical diodes have a cut-off frequency in the high gigahertz (GHz) or low terahertz (THz) range (e.g., a cut-off frequency less than 10 THz), which set a limit on the operating frequency range. Examples of such diodes include a Schottky diode, a backward tunneling diode, and a metal-insulator-metal (MIM) tunneling diode.
High-speed diodes, e.g., diodes having a cut-off frequency greater than 10 THz, are key elements for a broad range of applications. For example, a high speed diode combined with an optical antenna (referred as a rectenna) can lead to operations in optical frequencies, such as coherent generation and detection of infrared to far-infrared signals, and rectification of solar radiation for energy conversion. In these operations, the optical antenna is responsible for light collection and emission, while the diode must operate fast enough to match the corresponding optical frequencies and possess other required current-voltage (I-V) characteristics, such as excellent nonlinearity and rectification. Thus, obtaining highly nonlinear diodes having a cut-off frequency and operational speed higher than 100 THz is of profound technological and scientific importance.